Synthesis of meso-macro alumina using yeast cells as a bio-template and optimization using a genetic algorithm

Meso-Macro porous alumina was fabricated using yeast cells as a pore-forming agent. Alumina powder synthesis was achieved by a low cost process (recrystallisation of alum).The effect of the pore forming agent on the true porosity, bulk density and thermal conductivity of porous alumina was characterized. The results show that the true porosity increased with the increasi ng addition of yeast cells. The bulk density and thermal conductivity at room temperature decreased with the increasing yeast addition. A genetic algorithm method was used to minimize the thermal conductivity of the macro-porous alumina based on the amount of yeast cells used, the sintering temperature, and the hold time. The genetic algorithm found that the best thermal conductivity achievable was equal to 0.152 Watt/m. °C at 20wt% concentration of yeast, a sintering temperature of 1230°C and 1.5 hours of soaking time. The experimental value was 0.14 Watt/m. °C and the slight variance between these values were postulated to be due to experimental error in the measurements.     

Impact of combined moisture buffering capacity of a hemp concrete building envelope and interior objects on the hygrothermal performance in a room

In this article, a hygrothermal building model, taking into account the building envelope, indoor heat and moisture sources, indoor environment and moisture buffering capacity of interior objects, is presented and validated with the test cases found in the literature. The model is used to study the impact of hemp concrete and the moisture buffer capacity of the interior elements on the prediction of the hygrothermal comfort in the building. The numerical results show that the use of hemp concrete in buildings can ensure good hygrothermal comfort. Besides, taking into account the effect of moisture buffering of indoor objects increases the building performance. Our results also suggest that neglecting moisture transfer through the envelope increases significantly the predicted percentage of dissatisfied indices and reduces the acceptability of indoor air quality during the occupied period. This study also confirmed that the combined relative humidity-sensitive ventilation system and moisture buffering capacity of building envelope and of interior objects is a very efficient way to reduce the heating energy consumption.     

Maintenance integration in manufacturing systems by using stochastic Petri nets

Research into both increased performance and improvements in dependability of production systems involves maintenance integration, which allows one to protect their availability and their durability. In the case of large manufacturing systems, maintenance integration is essential from conception, and so it involves a particular development concerned with both model complexity and computing time. A modular modelling approach, based on a cellular decomposition of the system, using stochastic Petri nets and Markov chains has been adopted to implement various maintenance strategies in complex production workshops, with the aim of studying their influence on the system dependability and performance.     

F 11440, a potent, selective, high efficacy 5-HT1A receptor agonist with marked anxiolytic and antidepressant potential

F 11440 (4-methyl-2-[4-(4-(pyrimidin-2-yl)-piperazino)-butyl]-2H, 4H-1,2,4-triazin-3,5-dione) was the outcome of a research effort guided by the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their antidepressant and anxiolytic-like effects. The affinity of F 11440 for 5-HT1A binding sites (pKi, 8.33) was higher than that of buspirone (pKi, 7.50), and somewhat lower than that of flesinoxan (pKi, 8.91). In vivo, F 11440 was 4- to 20-fold more potent than flesinoxan, and 30- to 60-fold more potent than buspirone, in exerting 5-HT1A agonist activity at pre- and postsynaptic receptors in rats (measured by, for example, its ability to decrease hippocampal extracellular serotonin (5-HT) levels and to increase plasma corticosterone levels, respectively). F 11440 did not have detectable antidopaminergic activity (unlike buspirone, which inhibited all of the directly observable behavioral effects of methylphenidate in rats), showed no evidence of antihistaminergic activity (unlike flesinoxan, which protected against the effects of a histamine aerosol in guinea pigs), and had a 70-fold separation between its 5-HT1A agonist and alpha-1 adrenergic antagonist properties (measured as the ability to inhibit the methoxamineinduced increase in blood pressure in rats), unlike flesinoxan, which showed a <3-fold separation. In HeLa cells expressing human 5-HT1A receptors, F 11440 decreased the forskolin-induced increase in AMP, and, based on its maximal effect, was found to have an intrinsic activity of 1.0 relative to that of 5-HT, which was significantly higher than that of buspirone (0.49), ipsapirone (0.46) and flesinoxan (0.93). Consistent with the aforementioned hypothesis, F 11440 produced anxiolytic- and antidepressant-like effects in animal models (i.e., increased punished responding in a pigeon conflict procedure and decreased immobility in a rat forced swimming test, respectively) that were more substantial than those of buspirone, ipsapirone and flesinoxan. Thus, F 11440, shown here to be a potent, selective, high efficacy 5-HT1A receptor agonist, appears to have the potential to exert marked anxiolytic and antidepressant activity in humans.     

Amphoteric nature of vacancies in zinc blende semiconductors

We find that the donor-like properties of anion-site vacancies (and similarly the acceptor-like properties of cation-site vacancies) can be completely “inverted” through lattice relaxations leading to a dimerization of the dangling-bonds around a vacancy. On the basis of results obtained from first-principles total-energy calculations, we find that the amphoteric nature of anion-site vacancies plays an important role in dopant compensation and helps explain the difficulties encountered in the doping of some large band gap II–VI semiconductors.     

QoS-oriented resource allocation for streaming flows in?IEEE802.16e Mobile WiMAX

Users in OFDMA-based WiMAX are subject to Adaptive Modulation and Coding (AMC) which implies more robust and hence less frequency efficient modulation and coding for users experiencing bad radio conditions. When users are mobile, this implies lower throughput as they move away from the base station for instance. This may be acceptable for data users, but not for streaming ones which require a constant bit rate throughout the cell. We propose, in this work, a new QoS-oriented resource allocation strategy wherein streaming flows experiencing bad radio conditions are allocated more sub-carriers so as to keep their bit rate constant as they move around in the cell. The risk is however an increase in the dropping rate. To minimize the latter without increasing blocking too much, they are second subject to a state-dependent admission control scheme where the degree of acceptance depends on the density of the users in a given location. We develop an analytical model which allows us to derive some performance measures such as blocking and dropping probabilities. Our results quantify how these metrics vary with the load as well as the admission strategies.     

Novel architecture for high-pass cascaded ΔΣ modulator

High-pass (HP) delta-sigma (ΔΣ) modulators find utilisation in applications which are sensitive to low-frequency noises because of their complete immunity to these noises (Nguyen in High-pass DS modulator and its application to time-interleaved DS converter, Ecole Nationale Supérieur des télécommunications, PhD Dissertation, 2004). Single-stage HP ΔΣ modulator of order-2 has been presented in Nguyen et al. (Proceedings of ISCAS, 2006). This paper presents a novel approach for HP cascaded ΔΣ modulator, which attains better dynamic range, stability and achievable SNR than conventional cascade architecture. This approach has the flexibility of using any second-order HP ΔΣ modulator architecture in the first stage. We have used traditional HP ΔΣ modulator (Nguyen et al. in Proceedings of ISCAS, 2006) and the HP version of Silva structure (Silva et al. in Electron Lett 37(12):737–738, 2001) which has the additional advantages of reduced sensitivity to switch and op-amp nonlinearities and reduced op-amp voltage swings requirement as first stages of this new cascade technique. The first-stage made up of Silva-based feedforward HP structure proves to be a better choice because of its insensitivity to op-amp non-idealities. The method of designing cascade consists of approximating quantizer-gain by functional simulation of the modulator and then keeping this value in view while designing digital filters. Digital filters designed this way are more efficient in cancelling quantization error and provide better results. System level simulations have been performed in Matlab and transistor level simulations have been carried out in SPECTRE, both of which prove the efficacity of our approach.     

Combustion and air emissions from co‐firing a wood biomass,a Canadian peat and a Canadian lignite coal in a bubbling fluidised bed combustor

The effects of particle size, fuel blending ratio, moisture content and excess air ratio on combustion efficiency and air emissions (CO₂, CO, SO₂ and NO_x) from the co‐combustion of white pine or peat with a Canadian lignite coal, were examined in a pilot‐scale bubbling fluidised bed combustor. Pelletising was important for the efficient combustion of wood due to its high volatile content. Co‐firing lignite and pine pellets gave a proportional reduction in SO₂ and NO_x emissions with blending ratio, while co‐firing of peat and lignite resulted in increased SO₂ emissions, but decreased NO_x emissions. Moisture promotes combustion but with increased CO emissions, and results in increased NO_x emissions, and decreased SO₂ emissions. High excess air decreased CO, but moderately increased SO₂ and NO_x emissions. © 2011 Canadian Society for Chemical Engineering     

A new interpolation technique for time interleaved \Upsigma\Updelta A/D converters

Time interleaved sigma-delta converter is a potential candidate for multi-mode wideband analog to digital (A/D) converters dedicated for multistandard receivers. However, the interpolation by zeros to compress the useful signal bandwidth at the input of the sigma-delta modulator imposes constraints on the implementation of the analog part leading to a very large die area due to the high value required for the sampling capacitor. This paper proposes a new interpolation technique using extra samples instead of zeros resulting from the oversampling of the input signal. This new technique not only reduces the die area and the order of the anti-alias filter but also improves A/D converter performance. The proposed technique was simulated and implemented in a four channel time interleaved sigma-delta designed in a 1.2 V 65?nm CMOS process.